Bentley archives

Land Rovers

Thoughts on oil change intervals and other fluid matters

How often should you change the oil in your car? Should I follow the factory schedule? Sometimes people ask why I recommend deviating from the
factory service schedules for fluids in late model cars. I hope my thoughts on this matter will help you make a good decision for your own vehicle.

BMW and Mercedes introduced extended service intervals ten
years ago. Oil change intervals of
15,000 miles and even more were supposedly made possible by improvements in
engine design and new synthetic oil technology.

When people adhered to that schedule, the results were
mixed. People who drove on the highway,
and piled miles on quickly, often had good results. By “good” I mean they did not suffer any
lubrication related failures, and they got the economy of long oil changes.

People who drove mostly around town often had very different
experiences. Those cars often ended up
going a year and a half between services, and when we pulled the oil filters,
they were often nasty. A number of those
people had lube related problems – lifter noise, and worse.

That tells me the long intervals work for some people, but
not everyone. What’s the sensible
solution? Change your oil a bit more
often, with the very best available materials, and whichever kind of driver you
are, you should be safe.

With newer BMW, Mercedes, and Land Rover vehicles where a
15k oil change interval is recommended, I suggest reducing that interval to
10,000 miles or annually, whichever comes first. If you do that on a 2011 Land Rover,
Mercedes, or BMW, you will have an engine that’s just like new at 100k miles.

It is imperative to use the proper grade of synthetic oil
with the correct extended drain additive packages. Always make sure the oil you use meets the
specific requirements of your car. For
example, some Mercedes, use an oil that meets MB specification 229.51 while
others use a different spec. A wrong choice
could cost an engine.

The benefit of more frequent oil changes is extended engine
life and the avoidance of sludge damage in the motor. Since the cost of any such damage will run in
the thousands of dollars, that benefit is substantial. Offsetting that is the cost of the extra oil
changes. Over 100,000 miles, the extra
cost of 10k oil changes versus 15k changes might add up to $700. To me, that is a smart bet - $700 over 100k
miles to avoid a multi thousand dollar engine repair.

If you have an older car where the factory calls for 5,000 or 7,500 mile oil changes I suggest you stick to that but use a good synthetic. The synthetics have better detergents and they will keep your engine cleaner. At the same time, the synthetic formulations last far longer than 7,500 miles, so oil failure should never be an issue.

The only cars I suggest get more frequent services are antiques with limited filtration and/or sludge in the engines.

In any case, I suggest doing oil annually if the mileage targets are not reached.

More extended drain fluids are found in the transmission,
differentials, and power steering/hydraulics.
While synthetic oil technology has produced lubricants that should
last ten years or more, that does not mean I feel comfortable leaving them in a
car that long.

Few manual gearboxes, power steering systems, and
differentials have filters. That means
any contaminants that get into the oil keep making their way through the
system. If dirt gets in, or pieces of
metal invade the oil, disaster is ensured with those long change
intervals.

Another big risk is water intrusion. Differentials in particular are susceptible
to water intrusion. I’ve seen several
Mercedes 4Matic transfer cases that were ruined by watery lubricant as well.

For those reasons I suggest checking these fluids every 3
years-30,000 miles or wherever there is a visual suggestion of a problem.

Automatic transmissions are a different matter, because they
have filters. However, they also put
different stresses on their fluid, and having seen what gets drained out at
120,000 miles, I feel most ATF fluids should be done by 60k miles. The idea of “lifetime fill” simply means a
$5,000 repair if it blows up on your watch.
I’d rather up my odds and change the fluid every now and then. Note that most high-end cars use special
fluids and there are few if any generic substitutes.

What about brake fluid?
The reason for changing brake fluid is that it absorbs moisture, which
rusts brake components from the inside.
For many years, European carmakers suggested semi-annual fluid changes,
and domestic carmakers didn’t suggest any brake fluid service at all. The result was frozen calipers on domestics
and very little trouble on imports with fluid service.

There have not been any changes in brake fluid technology
and brake components are still made from similar materials as 20 years
ago. Therefore, I feel safe suggesting
we adhere to the traditional once-every-two-years fluid flush cycle. The exception to that is cars that get run on
the track, where the fluid gets hot, because the heat cycling can accelerate
moisture absorption. For cars that run
on the track I recommend annual flushes.

I think the fluid recommendations above represent a sensible
balance that favors extending the life of the vehicle’s mechanical systems at
minimal added maintenance cost. They are
based on my study of the cars and lubricants, and my 20-some years of
experience as a service manager here at J E Robison Service in
Springfield. However, the final decision
is up to you as the motorist.

1 comment:

Newer cars, using new, higher quality synthetic oils can definitely go a much greater distance without any need for change. 5000 miles is pretty much the minimum, and in many cases you can even go as much as 25k miles without a problem.

But the old mentalities are slow to die. The problem is simply that fact that most car users do not keep up with the technological advancements of engines and oils. It doesn't help that most car engines are so complicated these days that only professional mechanics can figure them out in the first place. So it almost doesn't pay to try and stay up to date unless it's your job or a big hobby.

But yeah, the truth is that frequent oil change is a waste of money, time and potentially causing harm to the environment due to the excess used oil waste that doesn't get recycled. http://www.fuelinjectorcleanerhq.com/correct-synthetic-oil-change-interval/

We are open from 8-5, Monday through Friday. There is a key drop in the front garage door for people who leave cars after hours.

We are New England's leading four-star authorized Bosch Car Service facility. Owner John Robison is a technical consultant to the Rolls Royce and Bentley owner clubs, the Land Rover club, and the BMW and Mercedes clubs. We're tech inspectors for the Porsche Club of America for regional track events. John's writing appears in many automotive magazines.